A lot will depend on how much of a stickler for accuracy you want to be. Since you have rejected Concorde, we assume that it is of
some concern
Assuming you can't swing for a Cubana paint job, then a nondescript livery is probably best. There may be anoraks in your audience ready to hoot and guffaw at your hero boarding an Emerald 748 (say) !
Couple of semi-anonymous DC-4s at North Weald might do. Now what would be REALLY neat would be to convince the Science Museum at Wroughton to roll out their TWA Connie for you. Ooooh.